Basic principles and a model
Posted: Wed Feb 03, 2010 8:05 am
The big picture: Ballparks and benchmarks
It's been a little while since I did a "big picture" post and explained just what it is that I see as the most plausible picture from the canon based on analysis from first principles. That is, we try to figure out what is underlying the mechanisms seen, and then determine the most reasonable capabilities based on that.
Building a model We assume the general case of L^6 ~ S^3 ~ V^2 ~ M^2 when data not available on st-v-sw.net and otherwise assume ISD-like proportions for SW ships based on available dimensional data, GCS-like proportions for a ST ship.
In Star Wars, highly efficient fusion is the name of the game. Larger ships require S (approximate surface area) greater area in shielding, which means that their shield strength increases per V/S with a V^1 investment in shield generators. Although they have V^1 times the fuel, they only have S~V^(2/3) times the surface area and a similar density of weapon emplacements. It would be reasonable to assume a typical designed mission duration proportionate to V^(1/3), which would complement a ~V^(2/3) rate of consumption. There are some problems associated with this, but I believe they can be accounted for using additional tactical factors and remain pernicious problems for any account of Star Wars.
EU support for these propositions: In the EU, we have the explicit baseline of combat power scaling per V^(1/3) and cost per V^(2/3) per the Strike Cruiser and similar fluff; we do indeed also have mission duration specifications scaling roughly on V^(1/3) - days to weeks for fighters, months to years for capital ships.
We will assume that Star Wars ships are fueled with heavy hydrocarbons producing 100 terajoules per liter in a fusion reaction of staggering efficiency. Hydrocarbon fuels burned with essentially magical fusion efficiencies remain, IMO, the best explanation for Star Wars technology on the highest level of canon. Alternate power sources may well exist, but are overall similarly effective.
We now consider sublight maneuverability. With the use of ion engines, the primary limiting factor of forward acceleration is more reactant mass than power. We will assume thrust scales with V. Thus, maximum linear acceleration will be presumed constant, in keeping with the TESB chase. Angular momentum, however, is V*L^2. Thus, rotational acceleration (in degrees per second squared) will decrease with L^2 (roughly).
We also apply a similar model to Star Trek. Several of our assumptions should be modified. Star Trek ships do not scale combat or mission endurance noticeably with size. A Constitution class seems to have a similar refuel and refit cycle as a Galaxy class. Thus, base firepower will scale directly with V. We will begin with the base case of the Galaxy class. We will assume that weapons output is 1% of maximum power output normally (we will consider some special cases, later). We will assume that 10% of the volume of a starship is given to fuel storage in both cases.
Baseline cases:
Take the iconic ship of Star Wars: The X-Wing starfighter. The total potential fuel capacity of the X-Wing is then 2700 liters, and the X-Wing carries fuel with a total energy value of 270 petajoules. Launching from and leaving an Earthlike planet at an Earthlike orbit around a Sunlike star requires only 0.1% of its fuel capacity. We assume, based on the lower hyperspace limit and a density like water, that the X-Wing is capable of putting out 10 terawatts at peak consumption. The X-Wing thus has fuel for 7.5 hours of maximum consumption. We will assume that 10% of peak instantaneous output may be directed towards weapons after accounting for system inefficiencies. This estimate then exceeds even the Wongian VFX-based overestimate of 600 GW, but is not unreasonable given the presumed power requirements of hyperdrive and the fuel capacity of the vehicle. We assume that a device providing 1 terajoule is capable of broaching the shields. (A VFX-based approach should fall two orders of magnitude lower.) We estimate turning speed generously at 180 degrees/sec^2, which represents the ability to perform a hard 180 in 2 seconds flat.)
For Star Trek, we begin with the best studied ship, the Galaxy class. Assume 580 million liters of M/AM storage at 14.2 PJ/L. This gives us 8.3 YJ of capacity, which lasts less than 6 hours at maximum power (this actually does not seem strange given the Enterprise's apparent ability to push itself to the breaking point in minutes when drawing maximum power from the warp coils). We take the minimum energy to breach the shields and deal bleed-through damage as 200 petajoules, i.e., a lower-end SB.com calculation for a photon torpedo. This is not at all realistic for what will bring down the shields, but it's worth making the point of comparison.
Is this fair? I think so. While the X-Wing would be able to drain its fuel with weapons in 75 hours, all Star Trek ships are then assumed to be able to do so in 575 hours; Star Trek ships seem to exhaust themselves more easily (see the E-E running out of torpedoes in its fight with the Scimitar). I think it is about as reasonable to place the GCS firepower at 4 EW as an X-Wing at 1 TW; both are generous given a VFX-based approach, but perfectly reasonable from first principles, and could be justified via reference to proton torpedoes and high end phaser drilling/photon torpedo spread incidents.
Model predictions:
Now, we examine the results of the model. Our model will provide general predictions - obviously, there are more complex factors in play. The obvious ship to check next is the Falcon:
The turn rate is a little low, but the Falcon is an exceptionally nimble ship for its size. We now dip into the EU, to consider the Victory Star Destroyer that starfighters keep bringing down in the EU books:
Given a proton torpedo yield of ~1 kiloton, it would take close to twenty proton torpedoes detonating in roughly the same place at roughly the same time to take down the Victory class's shields. Note that the Victory class is able to put that sort of energy out in a fraction of a second. Under this model, we have to assume that tactical factors prevent capital ships from effectively focusing firepower to take down each other's shields - it may be a question of the angular precision of weapons turrets and the use of many small weapons with distinct firing cycles, but it's a problem that needs to be considered in any version of the Star Wars universe that gives capital ships incredible firepower while still allowing fighters to threaten them.
Armor and structural durability should actually be quite significant in the Star Wars universe. One possibility that comes up frequently is the idea Star Wars shields are particularly vulnerable to torpedoes, due either to the very short time in which a proton torpedo detonates (microseconds) or due to the torpedo/fragments physically passing through shields designed to stop ray sections. Another is that capital ships' shields are somewhat diffuse and fighters actually fly through/under them when making attack runs. For the moment, though, we will leave the figures as they are.
Rotation is a more serious problem. While we should expect these larger ships to have far more trouble turning, they don't. Either their mass and thrusters are far better distributed, or they invest much more effort in being able to maneuver. We'll note this is a similar problem in Star Trek. Let's check the ISD, though:
Here, the ISD is beyond the reach of a single squadron of Rebel fighters. The firepower falls on the higher end of the range I outlined originally on my website based on the movies and VFX, although definitely within it. This is well above the firepower estimated for an ISD on ST-v-SW.net and well below the firepower estimated for an ISD on SDN. I've included for reference what V^(1/3) looks like about now - the ISD is supposed to be around 125 times as effective, overall, as the X-Wing, and is supposed to carry fuel and supplies for around a hundred times the mission duration. We now compare briefly to the MCC:
Here, our model has done something very clever that anticipates the EU's treatment of the ship. The SWRPG, for example, gives the MCC 20% more shields, which then regenerate twice as quickly; our model simply gives the MCC 40% more shields. The SWRPG gives the MCC 20 dice of turbolasers versus the ISD's 95, and 35 total dice of weapons vs the ISD's 107, i.e., 20-33% of the total firepower. Our model gives the MCC 24% of the total firepower.
The MCC has less surface area relative to its volume; our model interprets that as emphasizing shields over firepower. I still think the game statistics and similar statistics shortchange the MCC compared to its treatment in fiction, but this model happening to line them up is interesting. Now, we'll look at the Executor. Using the current "official" 19 km length, we would guess these to be its capabilities, from its baseline:
Almost 200 kilotons to take the shields down. In the EU, 300 proton torpedoes take down the Lusankya's shields and start damaging it; I think the firepower seems high based on its failure to blow up tons of Rebel ships in ROTJ, but it would be perfectly reasonable to assume firepower like that based on first principles. The shields may seem exceptionally fragile, but not unusually so if each little section is shielded independently.
Now we look at a few Star Trek ships. First, we take the Defiant and key its weapons up to 15% of its reactor power, rather than 1%:
Here, we see two things. First, the turn rate estimation - which worked out to be proportionate to 1/L^2, since moment of inertia was ~ ML^2 and thrust ~M - is completely absurd for Star Trek, just as it is for Star Wars. Smaller ships invest less in turning ability, larger ships more, and it breaks down rapidly. Second, the Defiant's firepower is actually pretty respectable. We'll compare it with Voyager:
Here we see just how amazing the Defiant is, pound for pound. Voyager is ten times the size, but if you can put 15% of your warp plasma towards weapons, the amount of firepower you can bring to the party goes up sharply. The Defiant carries more torpedoes, if anybody is counting - quantum torpedoes, at that - so Voyager getting the short end of the firepower comparison makes sense. The Defiant's shields are probably also overjuiced a little - probably not by a factor of fifteen, but they only need to be doubled from the strength expected of a "typical" ship their size and shape to match what we expect of Voygager's. For those of you putting photon torpedoes around 100 megatons, this puts Voyager's peak fighting output at ~1 photon torpedo per second, and the Defiant's at ~1.5.
Probably the most commonly appearing non-flagship class is the Excelsior, with 60 distinct appearances listed on Memory Alpha; it's also about average size for 24th century Federation starships, as far as we can tell. ST-v-SW.net gives two different models, one a little larger and bulkier:
For ~100 MT photon torpedoes that might be acceptable on, say, SB.com, that's 3 photon torpedoes every two seconds. Which is actually about what we see Excelsior class ships doing, in some scenes. However, our model predicts they are more fragile than the compact Defiant. Let's look at the Danube to see how this model extends for the smallest starships:
Now, compare and contrast to the Nebulon-B:
Even if the Nebulon was designed to blast through its fuel as quickly as the X-Wing, you'd still have less than 7 PW of effective weapon output. Fusion power is simply that anemic compared to antimatter power. Under a model that takes that into account, only the largest Star Wars ships can provide the firepower necessary to threaten a Star Trek ship - and the smallest of Star Trek ships is capable of pulling out photon torpedoes and blowing through any shields that a proton torpedo can threaten.
Analysis
These are all, of course, "first principles" ballpark estimates. It is reasonable to go back through and adjust specifically based on the balance of shielding to firepower to maneuverability - perhaps the Executor needs to invest more in maneuvering thrusters and less in firepower. Perhaps the Excelsior should go down in firepower and up in shielding. Some of the older ships may be more or less powerful across the board. The Sovereign class and Ambassador class are about the same overall size, but I'm pretty sure they don't have the same reactor rating. The Trade Federation battleship is clearly outclassed by ships a fraction of its size, so our first order estimate of its capabilities from first principles wouldn't be accurate at all.
There are assumptions in this model of Star Wars and Star Trek ships that are not "fair." That is, they seem to heavily penalize larger ships. At the same time, all of this makes sense in the EU and in the movies. A Saxtonian model where Star Destroyers wield proportionately similar or even more firepower than fighters simply cannot make sense of small attack craft. It cannot make sense of Rogue Squadron, and such a view also cannot make sense of the battles in ROTJ and ROTS. Or even TPM, for that matter.
It's all perfectly reasonable, and perfectly robust. You could perfectly reasonably place the shields higher for both franchises, and the firepower lower. Drop the ST firepower by more than an order of magnitude, and you start running into trouble with photon torpedoes. Raise the SW firepower by more than an order of magnitude, and you're going well beyond what proton torpedoes can provide for fighters (as well as very dramatically exceeding the VFX) - do both, and we have ISDs with firepower somewhere around the neigborhood of an Akira or Ambassador.
It's a problem. You can justify higher power generation by introducing exotic matter systems, but then you still have thermonuclear proton torpedoes. VFX problems may plague everyone, but at least Trek's VFX problems allow for multi-megaton firepower by its principal ships.
In Star Wars, it requires a great leap of faith to squeeze 600 GW out of an X-Wing shooting at the Death Star, or any more than a kiloton out of an exploding proton torpedo. If you squeeze hard, you can reasonably justify Star Destroyers competing with Klingon battlecruisers in bombardment capabilities. You can justify a Star Destroyer powerful enough to turbolaser a planetary civilization into oblivion. It's not hard, actually. But you can't justify a Star Destroyer that can ignore fighters freely, and because of that, you can't justify a Star Destroyer that can survive getting in a fight with a Galaxy class.
It's been a little while since I did a "big picture" post and explained just what it is that I see as the most plausible picture from the canon based on analysis from first principles. That is, we try to figure out what is underlying the mechanisms seen, and then determine the most reasonable capabilities based on that.
Building a model We assume the general case of L^6 ~ S^3 ~ V^2 ~ M^2 when data not available on st-v-sw.net and otherwise assume ISD-like proportions for SW ships based on available dimensional data, GCS-like proportions for a ST ship.
In Star Wars, highly efficient fusion is the name of the game. Larger ships require S (approximate surface area) greater area in shielding, which means that their shield strength increases per V/S with a V^1 investment in shield generators. Although they have V^1 times the fuel, they only have S~V^(2/3) times the surface area and a similar density of weapon emplacements. It would be reasonable to assume a typical designed mission duration proportionate to V^(1/3), which would complement a ~V^(2/3) rate of consumption. There are some problems associated with this, but I believe they can be accounted for using additional tactical factors and remain pernicious problems for any account of Star Wars.
EU support for these propositions: In the EU, we have the explicit baseline of combat power scaling per V^(1/3) and cost per V^(2/3) per the Strike Cruiser and similar fluff; we do indeed also have mission duration specifications scaling roughly on V^(1/3) - days to weeks for fighters, months to years for capital ships.
We will assume that Star Wars ships are fueled with heavy hydrocarbons producing 100 terajoules per liter in a fusion reaction of staggering efficiency. Hydrocarbon fuels burned with essentially magical fusion efficiencies remain, IMO, the best explanation for Star Wars technology on the highest level of canon. Alternate power sources may well exist, but are overall similarly effective.
We now consider sublight maneuverability. With the use of ion engines, the primary limiting factor of forward acceleration is more reactant mass than power. We will assume thrust scales with V. Thus, maximum linear acceleration will be presumed constant, in keeping with the TESB chase. Angular momentum, however, is V*L^2. Thus, rotational acceleration (in degrees per second squared) will decrease with L^2 (roughly).
We also apply a similar model to Star Trek. Several of our assumptions should be modified. Star Trek ships do not scale combat or mission endurance noticeably with size. A Constitution class seems to have a similar refuel and refit cycle as a Galaxy class. Thus, base firepower will scale directly with V. We will begin with the base case of the Galaxy class. We will assume that weapons output is 1% of maximum power output normally (we will consider some special cases, later). We will assume that 10% of the volume of a starship is given to fuel storage in both cases.
Baseline cases:
Take the iconic ship of Star Wars: The X-Wing starfighter. The total potential fuel capacity of the X-Wing is then 2700 liters, and the X-Wing carries fuel with a total energy value of 270 petajoules. Launching from and leaving an Earthlike planet at an Earthlike orbit around a Sunlike star requires only 0.1% of its fuel capacity. We assume, based on the lower hyperspace limit and a density like water, that the X-Wing is capable of putting out 10 terawatts at peak consumption. The X-Wing thus has fuel for 7.5 hours of maximum consumption. We will assume that 10% of peak instantaneous output may be directed towards weapons after accounting for system inefficiencies. This estimate then exceeds even the Wongian VFX-based overestimate of 600 GW, but is not unreasonable given the presumed power requirements of hyperdrive and the fuel capacity of the vehicle. We assume that a device providing 1 terajoule is capable of broaching the shields. (A VFX-based approach should fall two orders of magnitude lower.) We estimate turning speed generously at 180 degrees/sec^2, which represents the ability to perform a hard 180 in 2 seconds flat.)
Code: Select all
X-Wing:
Length: 12.5m
Effective weapon output: 1 TW
Endurance @ maximum power: 7.5 hours
Shielding: 1 TJ
Maximum rotational acceleration: 180 deg/sec^2Is this fair? I think so. While the X-Wing would be able to drain its fuel with weapons in 75 hours, all Star Trek ships are then assumed to be able to do so in 575 hours; Star Trek ships seem to exhaust themselves more easily (see the E-E running out of torpedoes in its fight with the Scimitar). I think it is about as reasonable to place the GCS firepower at 4 EW as an X-Wing at 1 TW; both are generous given a VFX-based approach, but perfectly reasonable from first principles, and could be justified via reference to proton torpedoes and high end phaser drilling/photon torpedo spread incidents.
Code: Select all
Galaxy class:
Length: 642m
Effective weapon output: 4 EW
Shielding: 200 PJ
Maximum rotational acceleration: 22.5 deg/sec^2Now, we examine the results of the model. Our model will provide general predictions - obviously, there are more complex factors in play. The obvious ship to check next is the Falcon:
Code: Select all
Millenium Falcon:
Length: 35m
Effective weapon output: 18 TW
Shielding: 8 TJ
Maximum rotational acceleration: 23 deg/sec^2Code: Select all
Victory Star Destroyer:
Length: 900m
Effective weapon output: 4.5 PW
Shielding: 79 TJ
Maximum rotational acceleration: 0.03 deg/sec^2Armor and structural durability should actually be quite significant in the Star Wars universe. One possibility that comes up frequently is the idea Star Wars shields are particularly vulnerable to torpedoes, due either to the very short time in which a proton torpedo detonates (microseconds) or due to the torpedo/fragments physically passing through shields designed to stop ray sections. Another is that capital ships' shields are somewhat diffuse and fighters actually fly through/under them when making attack runs. For the moment, though, we will leave the figures as they are.
Rotation is a more serious problem. While we should expect these larger ships to have far more trouble turning, they don't. Either their mass and thrusters are far better distributed, or they invest much more effort in being able to maneuver. We'll note this is a similar problem in Star Trek. Let's check the ISD, though:
Code: Select all
Imperial Star Destroyer:
Length: 1600m
Effective weapon output: 14 PW
Shielding: 140 TJ
Mission endurance (relative to X-Wing): 125Code: Select all
Mon Calamari Cruiser:
Length: 1200m
Effective weapon output: 3.4 PW
Shielding: 196 TJThe MCC has less surface area relative to its volume; our model interprets that as emphasizing shields over firepower. I still think the game statistics and similar statistics shortchange the MCC compared to its treatment in fiction, but this model happening to line them up is interesting. Now, we'll look at the Executor. Using the current "official" 19 km length, we would guess these to be its capabilities, from its baseline:
Code: Select all
Super Star Destroyer:
Length: 19 km
Effective weapon output: 784 PW
Shielding: 751 terajoulesNow we look at a few Star Trek ships. First, we take the Defiant and key its weapons up to 15% of its reactor power, rather than 1%:
Code: Select all
Defiant:
Length: 120m
Effective weapon output: 640 PW
Shielding: 55 petajoules
Turn rate: 644 deg/s^2Code: Select all
Voyager:
Length: 344m
Effective weapon output: 430 PW
Shielding: 109 petajoulesProbably the most commonly appearing non-flagship class is the Excelsior, with 60 distinct appearances listed on Memory Alpha; it's also about average size for 24th century Federation starships, as far as we can tell. ST-v-SW.net gives two different models, one a little larger and bulkier:
Code: Select all
Excelsior:
Length: 467-469m
Effective weapon output: 600-680 PW
Shielding: 42-43 petajoulesCode: Select all
Danube:
Length: 23m
Effective weapon output: 40 PW
Shielding: 4.7 petajoulesCode: Select all
Nebulon-B:
Length: 300m
Effective weapon output: 300 TW
Shielding: 23 terajoulesAnalysis
These are all, of course, "first principles" ballpark estimates. It is reasonable to go back through and adjust specifically based on the balance of shielding to firepower to maneuverability - perhaps the Executor needs to invest more in maneuvering thrusters and less in firepower. Perhaps the Excelsior should go down in firepower and up in shielding. Some of the older ships may be more or less powerful across the board. The Sovereign class and Ambassador class are about the same overall size, but I'm pretty sure they don't have the same reactor rating. The Trade Federation battleship is clearly outclassed by ships a fraction of its size, so our first order estimate of its capabilities from first principles wouldn't be accurate at all.
There are assumptions in this model of Star Wars and Star Trek ships that are not "fair." That is, they seem to heavily penalize larger ships. At the same time, all of this makes sense in the EU and in the movies. A Saxtonian model where Star Destroyers wield proportionately similar or even more firepower than fighters simply cannot make sense of small attack craft. It cannot make sense of Rogue Squadron, and such a view also cannot make sense of the battles in ROTJ and ROTS. Or even TPM, for that matter.
It's all perfectly reasonable, and perfectly robust. You could perfectly reasonably place the shields higher for both franchises, and the firepower lower. Drop the ST firepower by more than an order of magnitude, and you start running into trouble with photon torpedoes. Raise the SW firepower by more than an order of magnitude, and you're going well beyond what proton torpedoes can provide for fighters (as well as very dramatically exceeding the VFX) - do both, and we have ISDs with firepower somewhere around the neigborhood of an Akira or Ambassador.
It's a problem. You can justify higher power generation by introducing exotic matter systems, but then you still have thermonuclear proton torpedoes. VFX problems may plague everyone, but at least Trek's VFX problems allow for multi-megaton firepower by its principal ships.
In Star Wars, it requires a great leap of faith to squeeze 600 GW out of an X-Wing shooting at the Death Star, or any more than a kiloton out of an exploding proton torpedo. If you squeeze hard, you can reasonably justify Star Destroyers competing with Klingon battlecruisers in bombardment capabilities. You can justify a Star Destroyer powerful enough to turbolaser a planetary civilization into oblivion. It's not hard, actually. But you can't justify a Star Destroyer that can ignore fighters freely, and because of that, you can't justify a Star Destroyer that can survive getting in a fight with a Galaxy class.